KR20170074612A

KR20170074612A - Method for manufacturing iron-based powders

Info

Publication number: KR20170074612A
Application number: KR1020150184099A
Authority: KR
Inventors: 정은진; 강희수; 이언식; 신홍철; 권기혁
Original assignee: 주식회사 포스코; 재단법인 포항산업과학연구원
Priority date: 2015-12-22
Filing date: 2015-12-22
Publication date: 2017-06-30

Abstract

A method of manufacturing an iron-based powder, comprising the steps of: preparing an iron-based molten steel containing one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, and V; Injecting the molten steel into a tundish; Discharging molten steel through a nozzle connected to the tundish; And discharging the molten steel through a nozzle connected to the tundish, wherein the inside of the nozzle is controlled to be an inert gas and a hydrogen (H ₂ ) gas atmosphere, Wherein the spray liquid in the step of spraying water onto the discharged molten steel includes a rust inhibitor and the rust inhibitor is one or more of an amine compound, a phosphate compound, a nitrate compound, and a borate compound, By weight based on the total weight of the iron-based powder.

Description

METHOD FOR MANUFACTURING IRON-BASED POWDERS [0002]

Based powder.

Part manufacturing technology using powder is advantageous in increasing the dimensional accuracy of the final parts, facilitating mass production, and reducing machining and material loss.

In addition, since the component can be easily adjusted, the product performance can be maximized. Therefore, the importance of the technology as a core technology in the precision parts and materials manufacturing industry is greatly increasing.

Especially, by applying powder metallurgy process to automobile and electromechanical parts manufacturing, it can be produced at a cost of 40% or less compared with the conventional machining process.

Recently, with the development of the automobile and household appliances industries, the demand for sintered parts has increased, and the amount of powder used has increased rapidly. In order to manufacture sintered parts for automobiles, the powder itself must have high quality so as to produce high-density sintered bodies such as proper particle size, flowability, apparent density, molding density, and high cleanliness.

The existing iron-based powder manufacturing process is a water-spraying process in which molten metal is vertically dropped through a tundish and a molten metal nozzle using a converter or an electric furnace while spraying high-pressure water onto the molten metal to powder the molten metal, A dewatering and drying process for removing water by separating water, a reduction process for removing an oxide layer on the surface of the powder produced during the water injection process, and a crushing and mixing process.

In the case of preparing iron-based powders containing nano-reducible elements such as high manganese powder, it is advantageous to improve the physical properties of the sintered parts. However, since reduction is difficult, it is a key technology to improve the molding and sintering characteristics by controlling the oxygen concentration in the powder have. The reduction process for controlling the oxygen concentration in the powder is an important process that determines the composition and characteristics of the control powder, and it is also a process that requires a large expense in the entire process. It has the limitation that it can not improve the final productivity because it acts as a bottleneck process because the processing speed of the reducing process is the slowest in the whole manufacturing process.

Accordingly, it is necessary to design an efficient process for omitting the reduction process, which takes a large portion of the manufacturing cost, in order to improve the economical efficiency in the production of the iron-based powder containing the non-reducing element such as the high manganese powder.

An embodiment of the present invention is to provide a method of manufacturing an iron-based powder capable of minimizing an oxidation layer of a powder and omitting a reduction process, thereby improving the price competitiveness by simplifying the process. Further, one embodiment of the present invention is to provide a method for producing an iron-based powder having excellent quality such as high cleanliness and high molding density.

One embodiment of the present invention is a method of manufacturing a steel-made molten steel comprising the steps of: preparing an iron-based molten steel containing at least one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, and V; Injecting the molten steel into a tundish; Discharging molten steel through a nozzle connected to the tundish; And discharging the molten steel through a nozzle connected to the tundish, wherein the inside of the nozzle is controlled to be an inert gas and a hydrogen (H ₂ ) gas atmosphere, Wherein the spray liquid in the step of spraying water onto the discharged molten steel includes a rust inhibitor and the rust inhibitor is one or more of an amine compound, a phosphate compound, a nitrate compound, and a borate compound, By weight based on the total weight of the iron-based powder.

The content of at least one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, and V contained in the molten steel in the step of preparing the iron-based molten steel, May be 1% by weight or more, and 80% by weight or less based on 100% by weight of the total amount.

And discharging molten steel through a nozzle connected to the tundish, wherein the inert gas may be Ar, N ₂ , or a combination thereof.

Wherein the content of hydrogen (H ₂ ) gas in the nozzle is greater than or equal to 1 vol% and less than or equal to 100 vol% relative to a total volume of gas in the nozzle of 100 vol%, wherein the molten steel is discharged through a nozzle connected to the tundish, Or less.

In the step of spraying the molten steel to be discharged, the content of the rust inhibitor in the spray liquid may be 0.01 wt% or more and 5 wt% or less based on 100 wt% of the total amount of the sprayed liquid.

In the step of spraying water onto the discharged molten steel, the rustproofing agent may be a water-soluble or vapor-proof rustproofing agent.

And spraying water onto the discharged molten steel, the rustproofing agent may include triethanol amine, calcium phosphate, calcium nitrite, and calcium borate. have.

Spraying water onto the discharged molten steel; Thereafter, separating the iron-based powder and the water; And drying the separated iron-based powder.

The step of separating the iron-based powder and the water may be performed by dewatering the iron-based powder and the water for a time of 1 minute or more and 60 minutes or less.

The step of drying the separated iron-based powder may be performed by drying the separated iron-based powder at a temperature of 30 ° C or higher and 250 ° C or lower.

The step of drying the separated iron-based powder may be performed by drying the separated iron-based powder for 30 minutes or more and for 24 hours or less.

According to the method of manufacturing the iron-based powder according to an embodiment of the present invention, owing to the omission of the reduction step, the cost reduction effect of the powder production can be obtained, and accordingly, the production amount per unit time can be increased in the same equipment. Further, according to the method for producing an iron-based powder according to an embodiment of the present invention, it is possible to provide a powder having high quality such as high cleanliness and high molding density.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of a method for producing an iron-based powder according to an embodiment of the present invention. FIG.
2 is an optical microscope (OM) photograph of an iron-based powder prepared according to the conditions of Comparative Example 1 of the present invention.
3 is an optical microscope (OM) photograph of the iron-based powder prepared according to the conditions of Comparative Example 4 of the present invention.
4 is an optical microscope (OM) photograph of the iron-based powder prepared according to the conditions of Example 3 of the present invention.
5 is an optical microscope (OM) photograph of the iron-based powder prepared according to the conditions of Example 4 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

Generally, when an iron-based powder containing a highly reducing element such as a high manganese steel powder is prepared by water jetting, Fe + H ₂ O → FeO ₂ + H ₂ reaction occurs to have an unavoidable oxide layer on the surface. Therefore, it was possible to obtain a powder capable of achieving excellent moldability through an additional step for removing the oxide layer. The reduction process for controlling the oxygen concentration in the powder is an important process that determines the composition and characteristics of the control powder, and it is also a process that requires a large expense in the entire process. It has the limitation that it can not improve the final productivity because it acts as a bottleneck process because the processing speed of the reducing process is the slowest in the whole manufacturing process.

As a concrete example, conventionally, a process capable of simultaneously obtaining the oxide layer removal and the internal softening effect by keeping the hydrogen atmosphere in the continuous furnace heated to a temperature of about 800 ° C. or more and about 1,000 ° C. or more has been applied. However, And the process cost is increased due to the use of a large amount of expensive hydrogen.

In addition, in the case of the production of nano-reducing powders such as high manganese steel, the reduction of oxide layer in the powder was limited despite the use of hydrogen in a separate reduction process.

An embodiment of the present invention is to provide a method of manufacturing an iron-based powder capable of omitting the reduction process by controlling the atmosphere of water slush and using a water-soluble / vapor-proof rust preventive to solve the above problems.

FIG. 1 is a schematic structural view of a method of producing an iron-based powder according to an embodiment of the present invention. Hereinafter, a method for producing an iron-based powder according to an embodiment of the present invention will be described with reference to FIG.

One embodiment of the present invention is a method of manufacturing a steel-made molten steel comprising the steps of: preparing an iron-based molten steel containing at least one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, and V; (S10); Injecting the molten steel into the tundish (S20); Discharging molten steel through a nozzle connected to the tundish (S30); And a step (S40) to be injected into the molten steel in which the drain; step (S30) comprising a, and discharging the molten steel through a nozzle connected to the tundish; at the nozzle interior is an inert gas, and hydrogen (H ₂₎ (S40) of controlling the gas atmosphere and spraying the discharged molten steel with water, wherein the spray liquid contains an rust inhibitor, and the rust inhibitor is selected from the group consisting of an amine compound, a phosphate compound, a nitrate compound, and a borate compound Or a mixture of two or more of them. The present invention also provides a method for producing an iron-based powder.

The molten steel prepared in step (S10) of preparing the iron-based molten steel may be a molten steel of high manganese steel containing Mn as the non-reducible element in the range as described above. In addition, the molten steel may further include at least one of Si, Al, Mg, Ti, Zr, Ca, Cr, and V, or at least two non-reducible elements.

At this time, the content of at least one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, and V, or at least two of them, contained in the molten steel, , 1 wt% or more, and 80 wt% or less. More specifically not less than 10% by weight, and not more than 80% by weight; 10% or more, and 70% or less by weight; 10% or more, and 60% or less; 10% or more, and 50% or less by weight; 10% or more, and 40% or less; 10% or more, and 30% or less by weight; 10% or more, and 20% or less; 12% or more, and 20% or less by weight; 14% or more, and 20% or less; Or 16% by weight or more, and 20% or less by weight.

Step (S20) for discharging the molten steel through a nozzle connected to the tundish; in, the inert gas may be a combination of Ar, N _2, or combinations thereof. However, the present invention is not limited thereto, and other types of gases may be used as long as they are inert gases capable of forming an inert atmosphere. By controlling the nozzle in which the molten steel is discharged as described above to an inert atmosphere, the oxygen concentration in the molten steel can be lowered to suppress the formation of the oxide layer on the powder surface at the time of moisture.

The nozzle may further include hydrogen gas (H ₂ ) together with an inert gas. Hydrogen gas is further contained in the nozzle, so that a reducing atmosphere is formed, and oxidation of the surface of the molten steel at the time of moisture precipitation can be suppressed. At this time, the content of the hydrogen gas in the nozzle may be 1 vol% or more and 100 vol% or less with respect to 100 vol% of the total gas volume in the nozzle. More specifically at least 25 vol%, and at most 75 vol%; Or 30% by volume or more, and 60% by volume or less.

If the hydrogen content is too small, the oxide layer suppressing effect may be insignificant. If the hydrogen content is too large, the efficiency may be improved but the cost cost may increase.

(S40) of spraying water onto the discharged molten steel, wherein the spray liquid contains a rust inhibitor, and the rust inhibitor is at least one of an amine compound, a phosphate compound, a nitrate compound, and a borate compound, or 2 Or more species. More specifically, the rust inhibitor may be a water-soluble or vapor-barrier rust inhibitor.

Specifically, the amine compound may be a C1 to C10 primary amine, a C1 to C10 secondary amine, or a C1 to C10 tertiary amine. In the above-mentioned amine compounds, substituents such as a hydroxyl group (-OH) and a carboxy group (-COOH) may be substituted for the C1 to C10 carbon chain. More specifically, it may be triethanol amine.

Specifically, the phosphate compound may be a salt containing a phosphate (PO ₄ ^3- ), and more specifically, it may be calcium phosphate.

Specifically, the nitrate based compound may be a salt containing nitrate (NO ₂ ^- ), more specifically calcium nitrite.

Specifically, the borate compound may be a salt containing a borate (BO ₃ ^3- ), and more specifically, it may be a calcium borate.

These rust inhibitors have the property of controlling the interfacial tension in the powder and the degree of activation with moisture, and when used in the spray liquid at the time of water jetting, the generation of the oxide layer on the surface of the produced iron-based powder can be suppressed .

In addition, in the step S40 of spraying the discharged molten steel, the content of the rust inhibitor in the spray liquid may be 0.01 wt% or more and 5 wt% or less based on 100 wt% of the total amount of the sprayed liquid. More specifically, 0.5% by weight or more, and 5% by weight or less; Not less than 0.5% by weight, and not more than 3% by weight; Not less than 0.5% by weight, and not more than 4% by weight; Not less than 0.5% by weight, and not more than 2% by weight; 0.01% or more by weight; And 2% or less by weight; 0.01% or more by weight; And 2% or less by weight; Or 0.01% or more by weight; And 2% or less by weight.

If the content of the rust inhibitor in the spray liquid is too small, the rust prevention effect may be insignificant. If the content of the rust inhibitor in the spray liquid is 5% or more, there is no great difference in efficiency. .

The method of manufacturing an iron-based powder according to an embodiment of the present invention may include: spraying water onto discharged molten steel; Thereafter, separating the iron-based powder and the water; And drying the separated iron-based powder.

The step of separating the iron-based powder and the water may be performed by dewatering the iron-based powder and the water for a time of 1 minute or more and 60 minutes or less. However, this can be appropriately adjusted depending on the content of the powder to be produced, the amount of the sprayed liquid used when the water is used. If the dewatering time is too short, the moisture in the powder can not be sufficiently removed and the drying step may be delayed. If the dewatering time is longer than about 60 minutes, the water dewatering efficiency in the powder is lowered.

The step of drying the separated iron-based powder may be performed by drying the separated iron-based powder at a temperature of 30 ° C or higher and 250 ° C or lower. If the drying temperature is too low, there may arise a problem that moisture in the powder is not sufficiently removed. If the drying temperature is too high, the powder may be re-oxidized.

The step of drying the separated iron-based powder may be performed by drying the separated iron-based powder for 30 minutes or more and for 24 hours or less. If the drying time is too short, there is a problem that moisture in the powder is not sufficiently removed. If the drying time is too long, there may arise a problem in the drying furnace that can be re-oxidized together with oxygen in the furnace.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Examples and Comparative Examples: Preparation of iron-based powder

In the present production example, the influence of presence or absence of water-soluble and / Specifically, in order to prevent oxidation of the molten steel discharged through the tundish and the nozzle, the atmosphere of the nozzle before the water injection was controlled to an inert atmosphere and the oxidation of the powder was prevented by optimizing the use of the rust inhibitor. Through this, the reduction process was omitted by controlling the oxidizing atmosphere of the powder.

First, iron-based molten steel having the composition shown in Table 1 was prepared.

Then, the iron-based molten steel was injected into the tundish, and water injection was performed using a high-pressure water injector of 150 bar while dropping the molten steel through the nozzle.

In order to prevent the oxidation of the molten steel discharged through the tundish and the nozzle, the atmosphere of the nozzle before water injection was controlled to an inert gas and hydrogen atmosphere as shown in Table 2, and the rustproofing agent was optimally used for water spraying.

Vappro 849 (trade name: Polatec) containing an amine compound, a phosphate compound, a nitrate compound and a borate compound additive was used as a rust preventive agent, and a vapor permeable white powder rust preventive agent having a pH of about 7 was used.

After the completion of the water dispersion, the powder was dehydrated in the chamber in which the powder and water were leached for 10 minutes to remove moisture.

Thereafter, the obtained powder was dried at 150 DEG C for 24 hours to finally obtain an iron-based powder.

division Mn Fe Al Content (% by weight) 18 80.5 1.5

Experimental Example

Oxygen concentration of each powder was analyzed by N / O analyzer (LECO, Model: TC-600) after the water injection, and the cross section of each powder was analyzed by optical microscope (OM) to observe the oxide layer.

The oxygen concentration analysis results are shown in Table 3, and the optical microscope photographs are shown in FIG. 2 to FIG. Fig. 2 is a photograph of the iron-based powder prepared under the conditions of Comparative Example 1, Fig. 3, Comparative Example 4, Fig. 4, Example 3 and Fig.

As can be seen from Table 3, the oxygen concentration in the prepared iron-based powder was remarkably reduced by controlling the nozzle atmosphere with an inert gas (Ar, N ₂ ) and a reducing gas (H ₂ ).

As can be seen from Figs. 2 to 4, in Comparative Example 1 (Fig. 2) in which the atmosphere of the nozzle was set to ordinary air conditions and no rustproofing agent was used at the time of water leakage, it was found that the oxide layer was wide on the surface of the powder.

In the case of Comparative Example 4 (Fig. 3) in which the atmosphere of the nozzle was set to the ordinary air condition and the rust inhibitor was used at the time of water leakage, the oxide layer was reduced on the surface of the powder,

On the other hand, in the case of Example 4 (Fig. 5) in which the nozzle atmosphere was controlled in an inert and reducing atmosphere, and in Comparative Example 1 in which a rust preventive agent was used, It can be seen that the oxide layer on the powder surface is remarkably reduced as compared with Example 6.

Therefore, according to an embodiment of the present invention, it is possible to manufacture an iron-based powder having a low cost and a high purity as compared with a conventional iron-based powder production method by omitting the reduction process.

Spray atmosphere
(The content of each gas is volume%) (% By weight) Remarks Comparative Example 1 Air 100% - Molten steel temperature 1300 degrees or higher Comparative Example 2 0.5 Comparative Example 3 1.0 Comparative Example 4 2.0 Comparative Example 5 Ar 100% - Example 1 0.5 Example 2 1.0 Example 3 2.0 Comparative Example 6 Ar 50%, H ₂ 50% - Example 4 Ar 50%, H ₂ 50% 2.0

Spray atmosphere
(The content of each gas is volume%) (% By weight) Oxygen concentration in powder after water injection (% by weight) Comparative Example 1 Air 100% - 3.8 Comparative Example 2 0.5 3.2 Comparative Example 3 1.0 2.5 Comparative Example 4 2.0 1.8 Comparative Example 5 Ar 100% - 2.1 Example 1 0.5 1.6 Example 2 1.0 1.2 Example 3 2.0 0.6 Comparative Example 6 Ar 50%, H ₂ 50% - 2.0 Example 4 Ar 50%, H ₂ 50% 2.0 0.4

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims

Preparing an iron-based molten steel containing at least one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, and V, or at least two non-reducible elements;
Injecting the molten steel into a tundish;
Discharging molten steel through a nozzle connected to the tundish; And
And water spraying the discharged molten steel,
Step for discharging the molten steel through a nozzle connected to the tundish; from, the inside of the nozzle is controlled with an inert gas, and hydrogen (H ₂₎ gas atmosphere,
Wherein the spray liquid in the step of spraying water onto the discharged molten steel includes a rust inhibitor and the rust inhibitor is one or more of an amine compound, a phosphate compound, a nitrate compound, and a borate compound, Including,
A method for producing an iron-based powder.

The method of claim 1,
The content of at least one of Mn, Si, Al, Mg, Ti, Zr, Ca, Cr, and V contained in the molten steel in the step of preparing the iron-based molten steel,
By weight based on 100% by weight of the total amount of molten steel, and 80% by weight or less.
A method for producing an iron-based powder.

The method of claim 1,
Discharging molten steel through a nozzle connected to the tundish,
Wherein the inert gas is Ar, N _2, or to a combination thereof,
A method for producing an iron-based powder.

The method of claim 1,
Discharging molten steel through a nozzle connected to the tundish,
The content of the hydrogen (H ₂ ) gas in the nozzle is,
And not more than 1 volume%, and not more than 100 volume%, based on 100 volume% of the total gas volume in the nozzle.
A method for producing an iron-based powder.

The method of claim 1,
And injecting water into the discharged molten steel,
The content of the rust inhibitor in the spray liquid is,
By weight, and not more than 5% by weight based on 100% by weight of the total amount of spray liquid.
A method for producing an iron-based powder.

The method of claim 1,
And injecting water into the discharged molten steel,
The anti-
Soluble, or vapor-proof rust inhibitor.
A method for producing an iron-based powder.

The method of claim 1,
And injecting water into the discharged molten steel,
The anti-
Wherein the calcium phosphate is selected from the group consisting of triethanol amine, calcium phosphate, calcium nitrite, and calcium borate.
A method for producing an iron-based powder.

The method of claim 1,
Spraying water onto the discharged molten steel; Since the,
Separating the iron-based powder and the water; And
And drying the separated iron-based powder.
A method for producing an iron-based powder.

9. The method of claim 8,
Separating the iron-based powder and the water;
The iron-based powder and the water are dehydrated for 1 minute or more and 60 minutes or less,
A method for producing an iron-based powder.

9. The method of claim 8,
Drying the separated iron-based powder,
Wherein the separated iron-based powder is dried at a temperature of 30 ° C or higher and 250 ° C or lower.
A method for producing an iron-based powder.

11. The method of claim 10,
Drying the separated iron-based powder,
And the separated iron-based powder is dried for 30 minutes or more and for 24 hours or less.
A method for producing an iron-based powder.